The increased use of flat leadless surface mount components in electronic circuitry presents new challenges in the automated methods of soldering. Higher packing densities of surface mount components necessitates reduced solder joint size, volume, and, likewise, reduced spacing between solder joints. Since conventional through-hole insertion of components may be inappropriate for surface mounted components where both sides of the printed circuit board are used, other methods allowing for the accurate placement of components are required.
The geometry of conventional solder bumps presents problems in the placement and alignment of surface mounted components. U.S. Pat. No. 4,752,027 by Gschwend (and hereby incorporated by reference) discusses a method of flattening the peaks of solder bumps (by using rollers) for better alignment of surface mounted components on one side. Although the Gschwend method may improve the alignment of components in an automated system, other problems still remain. The warping of printed circuit boards due to thermal expansion and contraction, and solder splatter remains and may cause the misalignment of surface mounted components. Moreso, bottomside redoming of the solder joints remains a problem after reflow of the topside of the printed circuit board. In other words, bottomside flat joints sag into spherical joints again due to the reflow of the topside. Thus the problem of surface mount component misalignment and misplacement still remains.